CN108336176A - A kind of Si bases local emitter double-side solar cell structure - Google Patents

Abstract

A Si-based local emitter double-sided solar cell structure, with n-type crystalline silicon wafer as the substrate, the emitter surface is divided into emitter-conductive region and passivation-light-incoming region: the former is made of heavily doped p-type crystalline silicon The emitter layer and the metal gate line I are composed, and the heavily doped p-type crystalline silicon emitter layer has a smaller groove, while the metal gate line I has a slightly larger groove, and there is no heavy gap between the metal gate line I and the n-type crystalline silicon wafer. The area of the doped p-type crystalline silicon emitter layer is filled with a passivation anti-reflection layer I; the latter is composed of a heavily doped n-type crystalline silicon field passivation layer I and a passivation anti-reflection layer I; the back electric field surface is divided into passivation Chemical-incoming region and back electric field-conductive region: the former is composed of heavily doped n-type crystalline silicon layer II and passivation anti-reflection layer II; the latter is composed of heavily doped n-type crystalline silicon layer II and metal gate line II . The invention maintains the double-sided light-incoming characteristic of the crystalline silicon solar cell, obtains higher open-circuit voltage and short-circuit current, and improves the power generation capacity of the solar cell.

Description

A Si-based local emitter double-sided solar cell structure

technical field

The invention belongs to the fields of solar cells and semiconductor devices. It involves the preparation technology of solar cells.

Background technique

For double-sided crystalline silicon solar cells, the PERT structure has been focused on by the solar cell industry because of its good compatibility with the existing diffusion-junction crystalline silicon production line and its relatively high efficiency. However, the development of solar cells with this structure has encountered a bottleneck, one of which is the performance of the emitter layer formed by boron diffusion and its preparation technology. In order to achieve a higher open circuit voltage, the boron doping concentration must be high, but this will lead to an increase in carrier recombination. Moreover, the low square resistance required for the lateral transmission loss of carriers in the boron-doped layer is contradictory to the technical improvement direction of increasing the boron doping concentration (which will increase the recombination loss) required to achieve this condition.

How to solve this contradiction is crucial to the development of PERT technology, and we believe that starting from the design of the device structure may be an effective breakthrough. The present invention is a hard attempt in this direction.

Contents of the invention

The present invention is achieved through the following technical solutions.

A Si-based local emitter double-sided solar cell structure according to the present invention uses an n-type crystalline silicon wafer (5) as a substrate, and its emitter surface is divided into an emitter-conductive region and a passivation-light-incoming region: The emitter-conductive region is composed of a heavily doped p-type crystalline silicon emitter layer (2) and a metal gate line I (1) from the base to the outside, in which the heavily doped p-type crystalline silicon emitter layer (2) is grooved The metal gate line I (1) has a slightly larger slot, and there is no heavily doped p-type crystal silicon emitter layer (2) between the metal gate line I (1) and the n-type crystalline silicon wafer (5) It is filled with passivation anti-reflection layer I (3); the passivation-light entering area is composed of heavily doped n-type crystal silicon field passivation layer I (4) and passivation anti-reflection layer I (3) from the base to the outside . These two areas are intersected and do not overlap.

The passivation anti-reflection layer I (3) of the present invention is preferably silicon nitride.

Insulation treatment is preferably performed between the emitter described in the present invention and the heavily doped n-type crystalline silicon field passivation layer I (4).

Further, in order to improve the performance of the device, the thickness of the heavily doped n-type crystalline silicon field passivation layer I (4) is preferably 1-300 nm.

The Si-based local emitter double-sided solar cell structure described in the present invention is a double-sided light-incoming solar cell, and its positive and negative electrodes are respectively located on the two surfaces of the base of the n-type crystal silicon wafer (5). Into the light solar cells. The structure of the other side (back electric field surface) of the solar cell other than the emitter surface is divided into a passivation-light-incoming area and a back electric field-conductive area: the passivation-light-incoming area is heavily doped n-type crystal from the base to the outside Silicon layer II (6), passivation anti-reflection layer II (7); the back electric field-conductive region consists of heavily doped n-type crystalline silicon layer II (6) and metal gate line II (8) from the base to the outside. These two areas are intersected and do not overlap.

Wherein, the passivation anti-reflection layer II (7) is preferably silicon nitride.

Furthermore, in order to improve the performance of the device, the n-type crystalline silicon wafer (5) of the present invention can be textured on both sides, so as to further increase the short-circuit current of the solar cell.

Furthermore, the textures of both sides of the n-type crystalline silicon wafer (5) can be different, one side adopts a textured surface with a smaller size pyramid structure, and the other side adopts a larger size pyramid textured surface or a polished structure without pyramids.

Further, areas with metal grid lines (metal grid line I, metal grid line II) can be polished or made of larger-sized pyramid suede to reduce recombination loss and increase the open-circuit voltage of the solar cell.

Furthermore, the ratio of the total coverage area of the metal grid lines (metal grid lines I and metal grid lines II) on the device surface is preferably 1-3%, so as to improve the short-circuit current of the solar cell and ensure sufficient electrical conductivity.

The technical effect of the invention is that the invention is applicable to single crystal silicon wafer solar cells, polycrystalline silicon wafer solar cells and quasi-single crystal silicon wafer solar cells. On the premise of maintaining the double-sided light input characteristics of crystalline silicon solar cells, higher open-circuit voltage and short-circuit current are obtained, and the power generation capacity of crystalline silicon solar cells is improved to the greatest extent. The mechanism is to obtain a high open-circuit voltage through the p-type heavily doped crystalline silicon emitter and supporting structure under the coverage area of the metal grid line, because this structure can only consider the electrical properties of the emitter instead of the emitter layer in the PERT structure. It is also necessary to balance the degree of light absorption loss; in the place where there is no metal grid line, the structure of using a heavily doped n-type crystal silicon field passivation layer combined with a surface anti-reflection passivation layer is compared to the PERT full-surface heavily doped p-type layer combined with a passivation layer. The structure of the layer can reduce the short-circuit current and open-circuit voltage drop caused by the recombination loss of carriers. On the emitter surface, the generated photo-generated holes enter the bulk silicon under the push of the built-in electric field formed by the heavily doped n-type layer, and then flow concentratedly to the emitter region, forming a large current effect similar to a concentrating solar cell, which can Further increase the built-in potential of the solar cell, thereby further increasing the voltage of the solar cell; and the generated electrons can only flow to the metal electrode on the other side of the silicon wafer to be collected because there is no electrode in the heavily doped n-type region on the emitter surface.

Description of drawings

Accompanying drawing 1 is the schematic diagram of the present invention. Among them: 1 is the metal gate line I; 2 is the heavily doped p-type crystalline silicon layer; 3 is the passivation anti-reflection layer I; 4 is the heavily doped n-type crystalline silicon field passivation layer I; 5 is the n-type crystalline silicon 6 is the heavily doped n-type crystalline silicon layer II; 7 is the passivation anti-reflection layer II; 8 is the metal grid line II.

Detailed ways

The invention will be further illustrated by the following examples.

Example 1.

A Si-based local emitter double-sided solar cell structure as shown in FIG. 1 . Both sides of the n-type crystalline silicon wafer 5 adopt a pyramid structure suede surface with an average of ~2 microns, the thickness of the heavily doped n-type crystalline silicon field passivation layer I 4 is 10 nm, and the thickness of the heavily doped n-type crystalline silicon layer II 6 The passivation anti-reflection layer I 3 and passivation anti-reflection layer II 7 both use silicon nitride thin films, and the metal grid lines I 1 and metal grid lines II 8 both adopt the Ag grid line structure with the main and auxiliary grids. 3% of the surface area of the silicon wafer. The groove width of the metal gate line I1 is 30 μm, and the groove width of the heavily doped p-type crystalline silicon layer 2 is 20 μm. The structure has excellent double-sided light-incoming characteristics, that is, any side can be used as the main light-incoming surface. If it is used as a single-side light-incoming solar cell, a layer of metal can be plated on the backlight as a reflective layer to increase the short-circuit current of the single-side light-incoming solar cell. Preferably, the emitter surface is used as the main light-receiving surface.

Both surfaces of the structure have excellent light-incoming properties, and both surfaces can be used as main light-incoming surfaces. If it is used as a single-side light-incoming solar cell, a layer of metal can be plated on the backlight as a reflective layer to increase the short-circuit current of the single-side light-incoming solar cell.

Example 2.

A Si-based local emitter double-sided solar cell structure as shown in FIG. 1 . Both sides of the n-type crystalline silicon wafer 5 adopt a pyramid structure suede surface with an average of ~1 micron, the thickness of the heavily doped n-type crystalline silicon field passivation layer I 4 is 5 nm, and the thickness of the heavily doped n-type crystalline silicon layer II 6 The passivation anti-reflection layer I 3 and the passivation anti-reflection layer II 7 both use silicon oxide (10nm)/silicon nitride (80nm) composite films, and the metal grid lines I 1 and metal grid lines II 8 both use primary and secondary The grid-coordinated Ag grid line structure covers an area of 2% of the surface area of the silicon wafer. The groove width of the metal gate line I1 is 20 μm, and the groove width of the heavily doped p-type crystalline silicon layer 2 is 15 μm. The structure has excellent double-sided light-incoming characteristics, that is, any side can be used as the main light-incoming surface. If it is used as a single-side light-incoming solar cell, a layer of metal can be plated on the backlight as a reflective layer to increase the short-circuit current of the single-side light-incoming solar cell. Preferably, the emitter surface is used as the main light-receiving surface.

Both surfaces of the structure have excellent light-incoming properties, and both surfaces can be used as main light-incoming surfaces. If it is used as a single-side light-incoming solar cell, a layer of metal can be plated on the backlight as a reflective layer to increase the short-circuit current of the single-side light-incoming solar cell.

Example 3.

A Si-based local emitter double-sided solar cell structure as shown in FIG. 1 . Both sides of the n-type crystalline silicon wafer 5 adopt a pyramid structure suede surface with an average of ~3 microns, the thickness of the heavily doped n-type crystalline silicon field passivation layer I 4 is 50nm, and the thickness of the heavily doped n-type crystalline silicon layer II 6 220nm, passivation anti-reflection layer I 3 and passivation anti-reflection layer II 7 are made of silicon oxide (10nm) / silicon nitride (80nm) composite film, metal grid line I 1 and metal grid line II 8 are both primary and secondary The Ni/Ag composite grid line structure with the grid, the covering area is 2% of the surface area of the silicon wafer. The groove width of the metal gate line I1 is 40 μm, and the groove width of the heavily doped p-type crystalline silicon layer 2 is 30 μm. The structure has excellent double-sided light-incoming characteristics, that is, any side can be used as the main light-incoming surface. If it is used as a single-side light-incoming solar cell, a layer of metal can be plated on the backlight as a reflective layer to increase the short-circuit current of the single-side light-incoming solar cell. Preferably, the emitter surface is used as the main light-receiving surface.

Both surfaces of the structure have excellent light-incoming properties, and both surfaces can be used as main light-incoming surfaces. If it is used as a single-side light-incoming solar cell, a layer of metal can be plated on the backlight as a reflective layer to increase the short-circuit current of the single-side light-incoming solar cell.

Claims (9)

1. A Si-based local emitter double-sided solar cell structure, which is characterized in that an n-type crystalline silicon wafer (5) is used as a substrate, and its emitter surface is divided into an emitter-conductive region and a passivation-light-incoming region: The emitter-conductive region is composed of a heavily doped p-type crystalline silicon emitter layer (2) and a metal gate line I (1) from the base to the outside, in which the heavily doped p-type crystalline silicon emitter layer (2) is grooved Small, the metal gate line I (1) has a large slot, and the area between the metal gate line I (1) and the n-type crystalline silicon wafer (5) is not heavily doped p-type crystalline silicon emitter layer (2) by passivation The anti-reflection layer I (3) is filled; the passivation-light entering area is composed of a heavily doped n-type crystalline silicon field passivation layer I (4) and a passivation anti-reflection layer I (3) from the substrate to the outside. The regions are cross-distributed and do not overlap; The back electric field surface is divided into the passivation-light-incoming area and the back electric field-conductive area: the passivation-light-incoming area is from the base to the outside in order of heavily doped n-type crystalline silicon layer II (6), passivation anti-reflection layer II ( 7). The back electric field-conductive region is the heavily doped n-type crystalline silicon layer II (6) and the metal gate line II (8) from the base to the outside. These two regions cross and do not overlap. 2. A Si-based local emitter double-sided solar cell structure according to claim 1, characterized in that the passivation anti-reflection layer I (3) is silicon nitride. 3. A Si-based local emitter double-sided solar cell structure according to claim 1, characterized in that said emitter and heavily doped n-type crystalline silicon field passivation layer I (4) Insulation treatment. 4. A Si-based local emitter double-sided solar cell structure according to claim 1, characterized in that the thickness of the heavily doped n-type crystalline silicon field passivation layer I (4) is 1-300nm . 5. A Si-based local emitter double-sided solar cell structure according to claim 1, characterized in that the passivation anti-reflection layer II (7) is silicon nitride. 6. A Si-based local emitter double-sided solar cell structure according to claim 1, characterized in that the n-type crystalline silicon wafer (5) is textured on both sides. 7. A Si-based local emitter double-sided solar cell structure according to claim 1, characterized in that the double-sided texture of the n-type crystalline silicon wafer (5) is: one side adopts a small-sized pyramid Structured suede, large pyramid suede or polished structure without pyramids on the other side. 8. A Si-based local emitter double-sided solar cell structure according to claim 1, characterized in that the metal grid line area is polished or the suede surface of a large-scale pyramid is made. 9. A Si-based local emitter double-sided solar cell structure according to claim 1, characterized in that the total coverage ratio of metal grid lines on the surface of the device is 1-3%.